staging: crypto: skein: rename skein1024_ctx to skein_1024_ctx

Code have skein_512_ctx and skein_256_ctx but skein1024_ctx.
It would be logical to convert these names to a single form.

Signed-off-by: Anton Saraev <antonysaraev@gmail.com>
Reviewed-by: Jake Edge <jake@lwn.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>